Its also possible that the link mapper simply doesn't work. I ran the simpltest for it and it failed. Its unclear if the simpletests haven't been updated to drupal 7 or if the link mapper simplty doesn't work. The tests are at admin/config/development/testing when testing module is enabled.

I am experiencing a similar issue and could not import links from a cvs file. So, I wondered if this had to do with the specific format of the URl (youtube link) but tested on a random link and still no link being imported.
I am not sure how to go from there. Maybe one way would be use a different importer and overwrite content but I am dubious this would solve the problem.
Thanks
T

I kept getting corrupted YouTube links on import with SimplePie parser. The equals signs and ampersands in the links were being escaped, which broke the links. Switching to Common syndication parser and re -importing the feed items from YouTube fixed the problem.

EDITTED, IGNORE - I thought I was seeing this bug in alpha7, as link URLs were coming up blank while what I thought was identical logic mapped to other fields was being processed fine. Actually, there was a valid reason why it was coming up blank (preceding slash in xpath logic). So all is fine and works, I've re-closed this issue below.